Using traps

Traps provide an alternative to single steps through the program during execution. By setting traps at relevant portions of the program and checking values, it is possible to review the operation of a program without the time required to wade through single program steps.

Perhaps the most frequently-used program trap is the break trap, which always stops the program at a given point. Break traps are most useful when you wish to review results after a specific code section has been executed. The BREAK command can be used by positioning the cursor to the line to be stopped prior to executing the command, or by entering the statement number after the command (example: BREAK 551). Note that the numbers are those that appear on the compiler listing and are not related to the line numbers of the original program.

The INSIDE and OUTSIDE traps work with marked areas of the program, stopping execution whenever inside or outside the marked section. As with the BREAK trap, statement numbers may also be used (example: INSIDE 401 479). Another method is to mark specific sections and execute INSIDE or OUTSIDE without any other arguments.

The MODTRAP trap is one of the most useful of the traps. It allows you to review the contents of a register, address, or variable and stop execution whenever those contents change. The most practical use of this feature is in monitoring the behavior of variables, particularly those variables used as flags for state changes. For example, suppose you had the a variable that indicated whether a condition was met; the statement MODTRAP VARIABLE REC-FOUND-FLAG would stop program execution each time that a record was found and the variable changed.

Reducing keystrokes with Macros

The Debugger allows new commands to be defined as macros, functionally extended the command set. A macro consists of a single label and the commands that would be typed at the prompt. For example, a macro named STARTDSB could be defined to set up the screen like this:

DEFINE STARTDSB CURSOR DOWN 5; WINDOW 2

As you can see, multiple commands may be entered when separated by a semicolon. The label name should not be the name of a standard function; a macro defined with such a name removes that function from use. Macros can be removed by defining another with the same name, like this:

DEFINE STARTDSB STARTDSB

Macros can also be built into the standard DEBSTART (Debugger start) file or in private start files for your own use.

Summary

With its powerful search and trap facilities and integrated development tools, the Wang programming environment remains a comfortable workbench for the application programmer. Many of the features in the Wang Debugger are present in other COBOL environments, but rarely with the degree of integration found on the VS. Hopefully, this environment will be retained as Wang development moves to other environments.

I mentioned last time some that our shop had changed the standard DEBSTART file so that the PF keys were closer to Wang conventions. The modified table is shown in Figure 1, below. Naturally, other functions could be assigned to any of the keys according to your wishes.

Help with Winloc, WLOC setup

The April column on Winloc 3.1 stirred some interest among readers in problems configuring and using Wang's Windows-based terminal emulation products - particularly in combination with other products, including Wang's PCLIS, Macsoft's Lightspeed MVS products, and most any network software. Configuring Wang terminal cards and the Winloc software is not trivial; there are many situations where software and hardware conflicts can corrupt a network session or cause the PC to lock up, and seemingly harmless user behavior can precipitate a problem. I offer the following suggestions for setting up a Wang Local Office Connection (WLOC) card and software:

• Before attempting to set up a WLOC card or software, carefully review any information you have on memory and hardware interrupt usage for products you currently use. Compare this with the strap settings available for the WLOC card. Check this information with a utility that shows the actual interrupts used, such as MANIFEST (part of Quarterdeck's Expanded Memory Manager product (QEMM)) or Microsoft's MSD (bundled with Windows 3.1 or available from the Microsoft Download Service bulletin board (206-637-9009)).

• When setting up a WLOC card, start with the simplest configuration possible. Temporarily remark out any TSR (Terminate and Stay Resident) software from your AUTOEXEC.BAT and CONFIG.SYS files, and run the MS-DOS version of the terminal software if you have it. Add more items gradually until you reach a full configuration (or bomb out).

• Try to use the default WLOC board settings whenever possible. If you need to change the address of the board, change the I/O address first. Ignore the instructions that tell you to set the board for IRQ 5 or 7 for use with Windows.

• There were three generations of WLOC cards manufactured and each seems to work differently with certain PCs and applications. If you have the opportunity to exchange cards, see if that helps resolve any problems. If you are purchasing used cards from an equipment vendor, make compatibility with your applications a condition of product acceptance.

• If you have trouble getting enough conventional memory after setting up a WLOC card and are using a 386-class PC or better, consider using an expanded memory manager like QEMM (mentioned above) or Microsoft's MemMaker and EMM386. (MemMaker is a art of MS-DOS 6.0; EMM386 is shipped with Windows.)

• EMM386 has been known to conflict with Winloc, particularly on 386 machines with math coprocessors.

• If nothing else works, be prepared to produce a volume of information on your PC's configuration for the technical analysts - right down to the video and ROM-BIOS manufacturer, version, and date. Microsoft's MSD works well for this purpose.

(Thanks to my co-worker David Unruh for technical information on PC setups with Wang products.)

Do you have any other suggestions on configuring WLOC boards or related software? If so, forward them to me and I will pass them along.

Figure 1: Revised Version of DEBSTART

* * PF keys revised to match Wang key conventions better * and set up LISTING and DATA windows * assign 1 Variable assign 2 First assign 3 Last assign 4 Previous assign 5 Next assign 6 Previous 1 assign 7 Next 1 assign 8 Find assign 9 Search assign 10 Step 1 assign 11 Break assign 12 Delete assign 13 Help assign 14 Continue assign 15 Deactivate assign 16 Cancel assign 17 Clear assign 18 Data assign 19 Listing assign 20 Traps assign 21 State assign 22 Hex assign 23 Substring assign 24 Alter assign 25 Search Backward assign 26 Step Into 1 assign 27 Step Instruction 1 assign 28 Stacktrace assign 29 Training assign 30 Continue Trace assign 31 Activate assign 32 Close * * Set up window locations and types * Open with a LISTING window of five lines, with * the remaining area used for a DATA window. * Attributes are turned OFF for more data area. * w 3 attributes off cursor down 5 w 2